Along with surgery and radiotherapy, chemotherapy continues to be an effective therapy for many cancers. In fact, several types of cancer, such as Hodgkin""s disease, large cell lymphoma, acute lymphocytic leukemia, testicular cancer and early stage breast cancer, are now considered to be curable by chemotherapy. Other cancers such as ovarian cancer, small cell lung and advanced breast cancer, while not yet curable, are exhibiting positive response to combination chemotherapy.
One of the most important unsolved problems in cancer treatment is drug resistance. After selection for resistance to a single cytotoxic drug, cells may become cross resistant to a whole range of drugs with different structures and cellular targets, e.g., alkylating agents, antimetabolites, hormones, platinum-containing drugs, and natural products. This phenomenon is known as multidrug resistance (MDR). In some types of cells, this resistance is inherent, while in others, such as small cell lung cancer, it is usually acquired.
Such resistance is known to be multifactorial and is conferred by at least two proteins: the 170 kDa P-glycoprotein (MDR1) and the more recently identified 190 kDa multidrug resistance protein (MRP1). Although both MDR1 and MRP1 belong to the ATP-binding cassette superfamily of transport proteins, they are structurally very different molecules and share less than 15% amino acid homology. Despite the structural divergence between the two proteins, by 1994 there were no known consistent differences in the resistance patterns of MDR1 and MRP1 cell lines. However, the association, or lack thereof, of MRP1 and resistance to particular oncolytics is known. See Cole, et. al., xe2x80x9cPharmacological Characterization of Multidrug Resistant MRP-transfected Human Tumor Cellsxe2x80x9d, Cancer Research, 54:5902-5910, 1994. Doxorubicin, daunorubicin, epirubicin, vincristine, paclitaxel, mitoxantrone, melphalan, and etoposide are substrates of MRP1, i.e., MRP1 can bind to these oncolytics and redistribute them away from their site of action, the nucleus, and out of the cell. Id. and Marquardt, D., and Center, M. S., Cancer Research, 52:3157, 1992.
Doxorubicin, daunorubicin, and epirubicin are members of the anthracycline class of oncolytics. They are isolates of various strains of Streptomyces and act by inhibiting nucleic acid synthesis. These agents are useful in treating neoplasms of the bone, ovaries, bladder, thyroid, and especially the breast. They are also useful in the treatment of acute lymphoblastic and myeloblastic leukemia, Wilm""s tumor, neuroblastoma, soft tissue sarcoma, Hodgkin""s and non-Hodgkin""s lymphomas, and bronchogenic carcinoma.
Vincristine, a member of the vinca alkaloid class of oncolytics, is an isolate of a common flowering herb, the periwinkle plant (Vinca rosea Linn). The mechanism of action of vincristine is still under investigation but has been related to the inhibition of microtubule formation in the mitotic spindle. Vincristine is useful in the treatment of acute leukemia, Hodgkin""s disease, non-Hodgkin""s malignant lymphomas, rhabdomyosarcoma, neuroblastoma, and Wilm""s tumor.
Etoposide, a member of the epipodophyllotoxin class of oncolytics, is a semisynthetic derivative of podophyllotoxin. Etoposide acts as a topoisomerase inhibitor and is useful in the therapy of neoplasms of the testis, and lung.
It is presently unknown what determines whether a cell line will acquire resistance via a MDR1 or MRP1 mechanism. Due to the tissue specificity of these transporters and/or in the case where one mechanism predominates or is exclusive, it would be useful to have a selective inhibitor of that one over the other. Furthermore, when administering a drug or drugs that are substrates of either protein, it would be particularly advantageous to coadminister an agent that is a selective inhibitor of that protein. It is, therefore, desirable to provide compounds that are selective inhibitors of MDR1 or MRP1.
The present invention relates to a compound of formula: 
where:
A is a C3-C8 cycloalkyl, optionally substituted 1-3 times with a C1-C4 alkyl;
het is a five (5) membered heterocyclic ring comprising N and a second heteroatom selected from N, O, or S;
wherein the non-fused carbon atom of the heteroaryl ring may be optionally substituted with Rb: C1-C6 alkyl, optionally substituted aryl, optionally substituted heterocycle, an amino acid ester, CH2OH, CH2O-heterocycle, halo, CH2N3, CH2SR1, CH2NR4R6, OR1, SR13, S(CH2)k-phenyl, or NR4R6; provided that when het is pyrazole or imidazole, the saturated nitrogen of the het ring may be optionally substituted with Ra: C1-C4 alkyl;
k is 0, 1, 2, 3, or 4;
n is 0, 1, or 2;
p is 0 or 1;
q is 0, 1, or 2;
r is 0, 1, or 2;
t is 0, 1, 2, 3, or 4;
u is 0, 1, 2, 3, or 4;
Y is xe2x80x94Exe2x80x94C(O)R3, xe2x80x94Exe2x80x94CHxe2x95x90CHR13, xe2x80x94Exe2x80x94C(OH)R13, xe2x80x94Exe2x80x94NR4R5, xe2x80x94Exe2x80x94OR2, xe2x80x94Exe2x80x94S(O)qR13, xe2x80x94Exe2x80x94SO2NR4R6, xe2x80x94C(R11)xe2x95x90NR6, or an optionally substituted heterocycle;
E is a bond or xe2x80x94C(R11)(R11)xe2x80x94;
R1 is independently at each occurrence hydrogen or C1-C6 alkyl;
R2 is independently at each occurrence hydrogen, C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, or optionally substituted heterocycle, C(O)-aryl, or (CH2)2NR4R5;
R3 is independently at each occurrence hydrogen, C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted heterocycle, OR13, or NR4R6;
R4 is independently at each occurrence hydrogen, C1-C6 alkyl, optionally substituted (C1-C6 alkyl)-aryl, optionally substituted aryl, or R4 and R5, R6, R6xe2x80x2 combine to form xe2x95x90CR1R14;
R5 is independently at each occurrence hydrogen, C1-C6 alkyl, C1-C4 alkoxy, optionally substituted heterocycle, optionally substituted C3-C8 cycloalkyl, optionally substituted C6-C10 bicycloalkyl; optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle, C(O)C(O)R13, C(O)R7, CH2R7, SO2R8, a moiety of the formula 
or R4 and R5, together with the nitrogen to which they are attached, combine to form an optionally substituted N-heterocycle;
R6 is independently at each occurrence hydrogen, C1-C6 alkyl, C1-C4 alkoxy, optionally substituted C3-C8 cycloalkyl, optionally substituted C6-C10 bicycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted heterocycle, or R4 and R6, together with the nitrogen to which they are attached, combine to form an optionally substituted N-heterocycle;
R6xe2x80x2 is independently at each occurrence hydrogen, C1-C6 alkyl, C1-C4 alkoxy, optionally substituted C3-C8 cycloalkyl, optionally substituted C6-C10 bicycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted heterocycle, (C1-C4 alkyl)-OR13:
wherein the (C1-C4 alkyl) of the (C1-C4 alkyl)-OR13 may be optionally substituted from 1 to 2 times with C1-C4 alkyl, optionally substituted aryl, optionally substituted heterocycle;
or R4 and R6xe2x80x2, together with the nitrogen to which they are attached, combine to form an optionally substituted N-heterocycle;
R7 is independently at each occurrence optionally substituted C1-C6 alkyl, C1-C6 alkoxy, (C1-C4 alkoxy)-aryl, (C1-C4 alkoxy)-heterocycle, (C1-C4 alkoxy)-SiCH3, optionally substituted (C3-C8 cycloalkyl), optionally substituted (C1-C4 alkyl)-(C3-C8 cycloalkyl), optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, diphenylmethyl, optionally substituted (C1-C4 alkyl)-CO-aryl, optionally substituted CO-aryl, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted CHxe2x95x90CH-heterocycle, optionally substituted phenoxy, optionally substituted heterocycle, optionally substituted (C1-C4 alkyl)-phenoxy, (CH2)tS(O)rR1, (CH2)tC(R12)(R9)N(R16)(R15), (CH2)tC(R12)(R9)O(R17), (CH2)tC(R12)(R9)S(R17), or NR4R6xe2x80x2;
R8 is independently at each occurrence optionally substituted C1-C6 alkyl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted (C1-C4 alkyl)-heterocycle, or optionally substituted heterocycle;
R9 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted heterocycle, (CH2)u-(C1-C6 alkoxy), optionally substituted (CH2)uxe2x80x94Oxe2x80x94(C3-C8 cycloalkyl), optionally substituted (CH2)u-(C1-C4 alkoxy)-aryl, optionally substituted (CH2)uxe2x80x94O-aryl, optionally substituted (CH2)uxe2x80x94O-heterocycle, (C1-C4 alkyl)-CO2-(C1-C6 alkyl), optionally substituted (C1-C4 alkyl)-CO2-(C3-C8 cycloalkyl), optionally substituted (C1-C4 alkyl)-CO2-(C1-C4 alkyl)-aryl, optionally substituted (C1-C4 alkyl)-CO2-aryl, optionally substituted (C1-C4 alkyl)-CO2-heterocycle, or R9 and R12 can combine to form a C3-C8 cycloalkyl;
R10 is 0 to 4 substituents from the aryl ring independently at each occurrence hydrogen, halo, C(O)R3, cyano, optionally substituted heterocycle, optionally substituted aryl, Cxe2x89xa1Cxe2x80x94R1, C1-C4 alkoxy, (C1-C4 alkyl)-phenyl, NR19R20, or C2-C6 alkenyl;
R11 is independently at each occurrence hydrogen, C1-C6 alkyl, optionally substituted heterocycle, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted aryl, or optionally substituted (C1-C4 alkyl)-aryl;
R12 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle or optionally substituted heterocycle;
R13 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, CO2CH2CO2CH2CH3, or optionally substituted heterocycle;
R14 is independently at each occurrence C1-C6 alkyl or optionally substituted (C1-C4 alkyl)-aryl;
R15 is independently at each occurrence hydrogen, C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted C6-C10 bicycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted heterocycle, C(O)OR13, SO2R8, C(O)R18, or a moiety of the formula 
R16 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted aryl, optionally substituted heterocycle, SO2R8, or xe2x80x94COR8; or R16 and R15, together with the nitrogen to which they are attached, combine to form an optionally substituted N-heterocycle;
R17 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, COR18, optionally substituted heterocycle, optionally substituted (C1-C4 alkyl)-heterocycle, optionally substituted C1-C6 alkoxy, optionally substituted (C1-C4 alkoxy)-aryl, optionally substituted (C1-C4 alkoxy)-heterocycle, (C1-C4 alkyl)-N(R1)(R1), or an amino acid ester;
R18 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C4 alkyl)-aryl, optionally substituted aryl, optionally substituted heterocycle, (C1-C4 alkyl)-NHCO2-(C1-C4 alkyl), or optionally substituted (C1-C4 alkyl)-heterocycle;
R19 is independently at each occurrence hydrogen, or optionally substituted C1-C6 alkyl;
R20 is independently at each occurrence hydrogen, optionally substituted C1-C6 alkyl, CH2OH, COxe2x80x94(C1-C4 alkyl); or a pharmaceutical salt thereof.
The present invention further relates to a method of inhibiting MRP1 in a mammal which comprises administering to a mammal in need thereof an effective amount of a compound of formula I.
In another embodiment, the present invention relates to a method of inhibiting a resistant neoplasm, or a neoplasm susceptible to resistance in a mammal which comprises administering to a mammal in need thereof an effective amount of a compound of formula I in combination with an effective amount of an oncolytic agent.
The present invention also relates to a pharmaceutical formulation comprising a compound of formula I in combination with one or more oncolytics, pharmaceutical carriers, diluents, or excipients therefor.